1) Field of the Invention
The present invention relates to a rack structure for accommodating a plurality of electronic modules such as modulator-demodulators (modems) or the like.
2) Description of the Related Art
In general, an electronic module such as a modem or the like includes a flat box-like casing, and a printed circuit board housed in the casing, and the module is provided with terminals to be electrically connected to signal wires. When equipment comprising a plurality of electronic modules is necessary, these modules are accommodated side by side in a rack as books are arranged on a bookshelf. In this case, the terminals of each electronic module are formed as a plug including terminal pins, and the plug is connected to an outlet or receptacle attached to a backboard of the rack. Whenever each of the modules is accommodated in the rack, the connection between the plug and the receptacle must be ensured. To this end, the modules are guided in to position in the rack.
In particular, the rack includes a plurality of lower guide rails arranged side by side to form the bottom of the rack, and a plurality of upper guide rails arranged side by side to form the top of the rack. The lower guide rails and the upper guide rails are in vertical register with each other, respectively, and are vertically spaced apart from each other by a distance corresponding to a vertical width or height of the flat box-like casing of the module. Each of the lower guide rails has a pair of ridge elements coextended in parallel with each other and spaced from each other by a distance corresponding to a thickness of the flat box-like casing of the module, so that the pair of ridge elements defines a guide path for slidably receiving the lower side of the flat box-like casing of the module. Similarly, each of the upper guide rails also has a pair of ridge elements coextended in parallel with each other and spaced from each other by a distance corresponding to a thickness of the flat box-like casing of the module, so that the pair of ridge elements defines a guide path for slidably receiving the upper side of the flat box-like casing of the module. The accommodation of the module in the rack is carried out by engaging rear ends of the lower and upper sides of the flat box-like casing thereof with a set of the registered lower and upper guide rails, and by pushing in and sliding the same along the lower and upper guide rails until the plug of the module is connected to the corresponding receptacle provided on the backboard of the rack.
Of course, each of the lower and upper guide rails has an outer width larger than a thickness of the flat box-like casing of the modules, i.e., a pitch of the modules accommodated in the rack is larger than the thickness of the flat box-like casing thereof. Accordingly, the pitch of the modules must be made samll enough so that as many of the modules as possible can be accommodated in the rack. Nevertheless, conventionally it is impossible to make the pitch of the modules smaller due to the geometry of the flat box-like casing of the module, as mentioned hereinbefore in detail.
On the other hand, when each of the modules is accommodated and positioned in place in the rack so that the plug is connected to the corresponding receptacle, the module should be locked to be prevented from being unintentionally removed from the rack. To this end, the lower or upper guide rail has a resilient detent element integrally formed therewith. When the module is positioned in place in the rack, the resilient detent element is engaged with a front or outer end of the flat box-like casing to thereby prevent the unintentional removal of the module from the rack. Conventionally, the detent element is arranged to interfere with the accommodation of the module in the rack. Accordingly, the detent element must be moved out of the way before the module can be accommodated in the rack. This means that a person has both hands full for the accommodation of the module in the rack. Namely, one hand is used to move the detent element out of the way, and the other hand is used to push in the module along the guide rails. Further, the person has both hands full for intentionally removing a module from the rack. Namely, one hand is used for disengagement of the detent element from the box-like casing, and the other hand is used to pull the module out of the rack. All things considered, with the conventional arrangement of the detent element, the accommodation of the module in the rack as well as the removal of the module therefrom are both troublesome in that both hands must be used.